The present invention relates to a radioactive emission detector equipped with a position tracking system. More particularly, the present invention relates to the functional integration of a radioactive emission detector equipped with a position tracking system as above with medical imaging modalities and/or with guided minimally-invasive surgical instruments. The present invention is therefore useful for calculating the position of a concentrated radiopharmaceutical in the body in positional context of imaged portions of the body, which information can be used, for example, for performing an efficient minimally invasive surgical procedure. The present invention further relates to a surgical instrument equipped with a position tracking system and a radioactive emission detector for fine in situ localization during resection and/or biopsy procedures, which surgical instrument is operated in concert with other aspects of the invention.
The use of minimally invasive surgical techniques has dramatically affected the methods and outcomes of surgical procedures. Physically cutting through tissue and organs to visually expose surgical sites in conventional “open surgical” procedures causes tremendous blunt trauma and blood loss. Exposure of internal tissues and organs in this manner also dramatically increases the risk of infection. Trauma, blood loss, and infection all combine to extend recovery times, increase the rate of complications, and require a more intensive care and monitoring regiment. The result of such open surgical procedures is more pain and suffering, higher procedural costs, and greater risk of adverse outcomes.
In sharp contrast, minimally invasive surgical procedures cause little blunt trauma or blood loss and minimize the risk of infection by maintaining the body's natural barriers to infection substantially intact. Minimally invasive surgical procedures result in faster recovery and cause fewer complications than conventional, open, surgical procedures. Minimally invasive surgical procedures, such as laparoscopic, endoscopic, or cystoscopic surgeries, have replaced more invasive surgical procedures in all areas of surgical medicine. Due to technological advancements in areas such as fiber optics, micro-tool fabrication, imaging and material science, the physician performing the operation has easier-to-operate and more cost effective tools for use in minimally invasive procedures. However, there still exist a host of technical hurdles that limit the efficacy and increase the difficulty of minimally invasive procedures, some of which were overcome by the development of sophisticated imaging techniques. As is further detailed below the present invention offers a yet further advantage in this respect.
Radionuclide imaging is one of the most important applications of radioactivity in medicine. The purpose of radionuclide imaging is to obtain a distribution image of a radioactively labeled substance, e.g., a radiopharmaceutical, within the body following administration thereof to a patient. Examples of radiopharmaceuticals include monoclonal antibodies or other agents, e.g., fibrinogen or fluorodeoxyglucose, tagged with a radioactive isotope, e.g., 99Mtechnetium, 67gallium, 201thallium, 111indium, 123iodine, 125iodine and 18fluorine, which may be administered orally or intravenously. The radiopharmaceuticals are designed to concentrate in the area of a tumor, and the uptake of such radiopharmaceuticals in the active part of a tumor, or other pathologies such as an inflammation, is higher and more rapid than in the tissue that neighbors the tumor. Thereafter, a radiation emission detector, typically an invasive detector or a gamma camera (see below), is employed for locating the position of the active area. Another application is the detection of blood clots with radiopharmaceuticals such as ACUTECT from Nycomed Amersham for the detection of newly formed thrombosis in veins, or clots in arteries of the heart or brain, in an emergency or operating room. Yet other applications include radioimaging of myocardial infarct using agents such as radioactive anti-myosin antibodies, radioimaging specific cell types using radioactively tagged molecules (also known as molecular imaging), etc.
The distribution image of the radiopharmaceutical in and around a tumor, or another body structure, is obtained by recording the radioactive emission of the radiopharmaceutical with an external radiation detector placed at different locations outside the patient. The usual preferred emission for such applications is that of gamma rays, which emission is in the energy range of approximately 20-511 KeV. When the probe is placed in contact with the tissue, beta radiation and positrons may also be detected.
The first attempts at radionuclide “imaging” were in the late 1940's. An array of radiation detectors was positioned mechanically on a matrix of measuring points around the head of a patient. Alternatively, a single detector was positioned mechanically for separate measurements at each point on the matrix.
A significant advance occurred in the early 1950's with the introduction of the rectilinear scanner by Ben Cassen. With this instrument, the detector was scanned mechanically in a predetermined pattern over the area of interest.
The first gamma camera capable of recording all points of the image at one time was described by Hal Anger in 1953. Anger used a detector comprised of a NaI(Tl) screen and a sheet of X-ray film. In the late 1950's, Anger replaced the film screen with a photomultiplier tube assembly. The Anger camera is described in Hal O. Anger, “Radioisotope camera in Hine G J”, Instrumentation in Nuclear Medicine, New York, Academic Press 1967, chapter 19. U.S. Pat. No. 2,776,377 to Anger, issued in 1957, also describes such a radiation detector assembly.
U.S. Pat. No. 4,959,547 to Carroll et al. describes a probe used to map or provide imaging of radiation within a patient. The probe comprises a radiation detector and an adjustment mechanism for adjusting the solid angle through which radiation may pass to the detector, the solid angle being continuously variable. The probe is constructed so that the only radiation reaching the detector is that which is within the solid angle. By adjusting the solid angle from a maximum to a minimum while moving the probe adjacent the source of radiation and sensing the detected radiation, one is able to locate the probe at the source of radiation. The probe can be used to determine the location of the radioactivity and to provide a point-by-point image of the radiation source or data for mapping the same.
U.S. Pat. No. 5,246,005 to Carroll et al. describes a radiation detector or probe, which uses statistically valid signals to detect radiation signals from tissue. The output of a radiation detector is a series of pulses, which are counted for a predetermined amount of time. At least two count ranges are defined by circuitry in the apparatus and the count range which includes the input count is determined. For each count range, an audible signal is produced which is audibly discriminable from the audible signal produced for every other count range. The mean values of each count range are chosen to be statistically different, e.g., 1, 2, or 3 standard deviations, from the mean of adjacent lower or higher count ranges. The parameters of the audible signal, such as frequency, voice, repetition rate, and/or intensity are changed for each count range to provide a signal which is discriminable from the signals of any other count range.
U.S. Pat. No. 5,475,219 to Olson describes a system for detecting photon emissions wherein a detector serves to derive electrical parameter signals having amplitudes corresponding with the detected energy of the photon emissions and other signal generating events. Two comparator networks employed within an energy window, which define a function to develop an output, L, when an event-based signal amplitude is equal to or above a threshold value, and to develop an output, H, when such signal amplitude additionally extends above an upper limit. Improved reliability and accuracy is achieved with a discriminator circuit which, in response to these outputs L and H, derives an event output upon the occurrence of an output L in the absence of an output H. This discriminator circuit is an asynchronous, sequential, fundamental mode discriminator circuit with three stable states.
U.S. Pat. Nos. 5,694,933 and 6,135,955 to Madden et al. describe a system and method for diagnostic testing of a structure within a patient's body that has been provided with a radioactive imaging agent, e.g., a radiotracer, to cause the structure to produce gamma rays, associated characteristic x rays, and a continuum of Compton-scattered photons. The system includes a radiation receiving device, e.g., a hand-held probe or camera, an associated signal processor, and an analyzer. The radiation receiving device is arranged to be located adjacent the body and the structure for receiving gamma rays and characteristic X-rays emitted from the structure and for providing a processed electrical signal representative thereof. The processed electrical signal includes a first portion representing the characteristic X-rays received and a second portion representing the gamma rays received. The signal processor removes the signal corresponding to the Compton-scattered photons from the electrical signal in the region of the full-energy gamma ray and the characteristic X-ray. The analyzer is arranged to selectively use the X-ray portion of the processed signal to provide near-field information about the structure, to selectively use both the X-ray and the gamma-ray portions of the processed signal to provide near-field and far-field information about the structure, and to selectively use the gamma-ray portion of the processed signal to provide extended field information about the structure.
U.S. Pat. No. 5,732,704 to Thurston et al. describes a method for identifying a sentinel lymph node located within a grouping of regional nodes at a lymph drainage basin associated with neoplastic tissue wherein a radiopharmaceutical is injected at the situs of the neoplastic tissue. This radiopharmaceutical migrates along a lymph duct towards the drainage basin containing the sentinel node. A hand-held probe with a forwardly disposed radiation detector crystal is maneuvered along the duct while the clinician observes a graphical readout of count rate amplitudes to determine when the probe is aligned with the duct. The region containing the sentinel node is identified when the count rate at the probe substantially increases. Following surgical incision, the probe is maneuvered utilizing a sound output in connection with actuation of the probe to establish increasing count rate thresholds followed by incremental movements until the threshold is not reached and no sound cue is given to the surgeon. At this point of the maneuvering of the probe, the probe detector will be in adjacency with the sentinel node, which then may be removed.
U.S. Pat. No. 5,857,463 to Thurston et al. describes further apparatus for tracking a radiopharmaceutical present within the lymph duct and for locating the sentinel node within which the radiopharmaceutical has concentrated. A smaller, straight, hand-held probe is employed carrying two hand actuable switches. For tracking procedures, the probe is moved in an undulatory manner, wherein the location of the radiopharmaceutical-containing duct is determined by observing a graphics readout. When the region of the sentinel node is approached, a switch on the probe device is actuated by the surgeon to carry out a sequence of squelching operations until a small node locating region is defined.
U.S. Pat. No. 5,916,167 to Kramer et al. and U.S. Pat. No. 5,987,350 to Thurston describe surgical probes wherein a heat-sterilizable and reusable detector component is combined with a disposable handle and cable assembly. The reusable detector component incorporates a detector crystal and associated mountings along with preamplifier components.
U.S. Pat. No. 5,928,150 to Call describes a system for detecting emissions from a radiopharmaceutical injected within a lymph duct wherein a hand-held probe is utilized. When employed to locate sentinel lymph nodes, supplementary features are provided including a function for treating validated photon event pulses to determine count rate level signals. The system includes a function for count-rate based ranging as well as an adjustable thresholding feature. A post-threshold amplification circuit develops full-scale aural and visual outputs.
U.S. Pat. Nos. 5,932,879 and 6,076,009 to Raylman et al. describe an intraoperative system for preferentially detecting beta radiation over gamma radiation emitted from a radiopharmaceutical. The system has ion-implanted silicon charged-particle detectors for generating signals in response to received beta particles. A preamplifier is located in proximity to the detector filters and amplifies the signal. The probe is coupled to a processing unit for amplifying and filtering the signal.
U.S. Pat. No. 6,144,876 to Bouton describes a system for detecting and locating sources of radiation, with particular applicability to interoperative lymphatic mapping (ILM) procedures. The scanning probe employed with the system performs with both an audible as well as a visual perceptive output. A desirable stability is achieved in the readouts from the system through a signal processing approach which establishes a floating or dynamic window analysis of validated photon event counts. This floating window is defined between an upper edge and a lower edge. The values of these window edges vary during the analysis in response to compiled count sum values. In general, the upper and lower edges are spaced apart a value corresponding with about four standard deviations.
To compute these count sums, counts are collected over successive short scan intervals of 50 milliseconds and the count segments resulting therefrom are located in a succession of bins within a circular buffer memory. The count sum is generated as the sum of the memory segment count values of a certain number of the bins or segments of memory. Alteration of the floating window occurs when the count sum either exceeds its upper edge or falls below its lower edge. A reported mean, computed with respect to the window edge that is crossed, is developed for each scan interval which, in turn, is utilized to derive a mean count rate signal. The resulting perceptive output exhibits a desirable stability, particularly under conditions wherein the probe detector is in a direct confrontational geometry with a radiation source.
U.S. Pat. No. 5,846,513 teaches a system for detecting and destroying living tumor tissue within the body of a living being. The system is arranged to be used with a tumor localizing radiopharmaceutical. The system includes a percutaneously insertable radiation detecting probe, an associated analyzer, and a percutaneously insertable tumor removing instrument, e.g., a resectoscope. The radiation detecting probe includes a needle unit having a radiation sensor component therein and a handle to which the needle unit is releasably mounted. The needle is arranged to be inserted through a small percutaneous portal into the patient's body and is movable to various positions within the suspected tumor to detect the presence of radiation indicative of cancerous tissue. The probe can then be removed and the tumor removing instrument inserted through the portal to destroy and/or remove the cancerous tissue. The instrument not only destroys the tagged tissue, but also removes it from the body of the being so that it can be assayed for radiation to confirm that the removed tissue is cancerous and not healthy tissue. A collimator may be used with the probe to establish the probe's field of view.
The main limitation of the system is that once the body is penetrated, scanning capabilities are limited to a translational movement along the line of penetration.
An effective collimator for gamma radiation must be several mm in thickness and therefore an effective collimator for high energy gamma radiation cannot be engaged with a fine surgical instrument such as a surgical needle. On the other hand, beta radiation is absorbed mainly due to its chemical reactivity after passage of about 0.2-3 mm through biological tissue. Thus, the system described in U.S. Pat. No. 5,846,513 cannot efficiently employ high energy gamma detection because directionality will to a great extent be lost and it also cannot efficiently employ beta radiation because too high proximity to the radioactive source is required, whereas body tissue limits the degree of maneuvering the instrument.
The manipulation of soft tissue organs requires visualization (imaging) techniques such as computerized tomography (CT), fluoroscopy (X-ray fluoroscopy), magnetic resonance imaging (MRI), optical endoscopy, mammography or ultrasound which distinguish the borders and shapes of soft tissue organs or masses. Over the years, medical imaging has become a vital part in the early detection, diagnosis and treatment of cancer and other diseases. In some cases medical imaging is the first step in preventing the spread of cancer through early detection and in many cases medical imaging makes it possible to cure or eliminate the cancer altogether via subsequent treatment.
An evaluation of the presence or absence of tumor metastasis or invasion has been a major determinant for the achievement of an effective treatment for cancer patients. Studies have determined that about 30% of patients with essentially newly diagnosed tumor will exhibit clinically detectable metastasis. Of the remaining 70% of such patients who are deemed “clinically free” of metastasis, about one-half are curable by local tumor therapy alone. However, some of these metastasis or even early stage primary tumors do not show with the imaging tools described above. Moreover often enough the most important part of a tumor to be removed for biopsy or surgically removed is the active, i.e., growing part, whereas using only conventional imaging cannot distinguish this specific part of a tumor from other parts thereof and/or adjacent non affected tissue.
A common practice in order to locate this active part is to mark it with radioactivity tagged materials generally known as radiopharmaceuticals, which are administered orally or intravenously and which tend to concentrate in such areas, as the uptake of such radiopharmaceuticals in the active part of a tumor is higher and more rapid than in the neighboring tumor tissue. Thereafter, a radiation emission detector, typically an invasive detector, is employed for locating the position of the active area.
Medical imaging is often used to build computer models which allow doctors to, for example, guide exact radiation in the treatment of cancer, and to design minimally-invasive or open surgical procedures. Moreover, imaging modalities are also used to guide surgeons to the target area inside the patient's body, in the operation room during the surgical procedure. Such procedures may include, for example, biopsies, inserting a localized radiation source for direct treatment of a cancerous lesion, known as brachytherapy (so as to prevent radiation damage to tissues near the lesion), injecting a chemotherapy agent into the cancerous site or removing a cancerous or other lesions.
The aim of all such procedures is to pin-point the target area as precisely as possible in order to get the most precise biopsy results, preferably from the most active part of a tumor, or to remove such a tumor in its entirety on the one hand with minimal damage to the surrounding, non affected tissues, on the other hand.
However, in the current state of the prior art this goal is yet to be achieved, as most of the common imaging modalities such as fluoroscopy, CT, MRI, mammography or ultrasound demonstrate the position and appearance of the entire lesion with anatomical modifications that the lesion causes to its surrounding tissue, without differentiating between the non-active mass from the physiologically active part thereof.
On the other hand, prior art radiation emission detectors and/or biopsy probes, while being suitable for identifying the location of the radiation site, they leave something to be desired from the standpoint of facilitating the removal or other destruction of the detected cancerous tissue with minimum invasion of the patient.
The combination of modalities, as is offered by the present invention, can reduce the margin of error in positioning such tumors. In addition, the possibility of demonstrating the position of the active part of a tumor superimposed on a scan from an imaging modality that shows the organ or tumor, coupled with the possibility to follow a surgical tool in reference to the afflicted area during a surgical procedure will allow for a more precise and controlled surgical procedures to take place, minimizing the aforementioned problems.
The present invention addresses these and other issues which are further elaborated hereinbelow, and offers the physicians and patients more reliable targeting, that in turn will result in less invasive and less destructive surgical procedures and less cases of mistaken diagnosis.